Search

A pointwise explosive-induced pyroshock prediction scheme based on the numerical conditioning of laser shocks is proposed to nondestructively predict a point source pyroshock at any point. In the pyroshock prediction scheme, the estimation models of the subband envelopes of pyroshocks incorporated into the signal processing algorithm were used to numerically condition the laser shocks. The conditioned laser shocks showed the ability to predict the SRS and time-domain waveform of pyroshock signals at any point with the averaged mean acceleration difference (MAD) of 27.25 % and the averaged peak-to-peak acceleration difference (PAD) of 18.13 % respectively. Using the prediction scheme, two-dimensional (2-D) spatial conditioned laser shocks were obtained and used to visualize the pyroshock wave propagation in an interest area of 100 × 100 mm2.

Waves induced by impact initiate deformation mechanisms within a material that precede later flow. An impulse excites a cascade of deformation mechanisms starting with ultrafast and concluding with slower ones. In metals, brittle glasses and polycrystalline ceramics there are a combination of mechanisms with differing relaxation times that condition a loaded target. In the case of ballistic impact, once failure has occurred, long rod penetration can occur and the depth achieved within each target can be scaled with the deformation strengths recorded during the initial high pressure impulse. A review of material shock response and target preconditioning shows a correlation with the ballistic penetration of the target after loading. This indicates that the effect of an initial loading impulse upon material behaviour is a strong feature of the effects observed in many dynamic phenomena.

High-frequency ground motions (referred to as “ground shocks”) of potentially damaging magnitude are produced from blasting and heavy construction activities. Up to now, quantification of the ground shock response and damage has remained empirical on the basis of general field observations. Systematic test data that allow for a rigorous interpretation of the response characteristics and calibration of analytical models are scarce. In this investigation, a unique experimental program was conducted to simulate the ground shock response on scaled reinforced concrete frame models with an electromagnetic shaker. Different response characteristics under high frequency excitations as compared to the familiar earthquake response are observed. In particular, the structural significance of local modes in high frequency response is clearly identified. The measured response allowed for the construction of spectral concrete strain curves for a given ground motion peak particle velocity (PPV), based on which a benchmark allowable PPV vs. input frequency relationship is obtained and is compared with relevant code provisions.

Existing design rules for tank vehicles have proved insufficient, because vibrations often cause fatigue cracks. Measurements have been performed on the tank to provide a picture of the influence of different road types and filling ratios. Shock response spectrum analysis (SRS) was used to obtain a measure of single-dynamic events. To get a basis for dimensioning against fatigue a calculation of fatigue-damage response spectra (FDRS) has been performed. This relates the vibrations in the tank to the risk of fatigue damage. In lieu of cycle counting by rain-flow count techniques, which has certain disadvantages, a new model, the so called HdM model, for fatigue-life assessment based on level crossing has been used. Further development of the results of the analysis can be used to improve design criteria in transport tank regulations, as well as to determine optimum inspection intervals for, in particular, tanks for hazardous materials.